Gov. John N. Dalton refused today to commit 40 percent of the state's emergency gasoline supply to Northern Virginia for August, as he did for July.

Dalton pledged to use the emergency supply to prevent gasoline lines from recurring in Northern Virginia and also said he would continue the area's odd-even rationing system for "the immediate future."

Citing what he called "worsening problems" in some rural areas, Dalton stopped short of pledging a specific amount of the state's setaside supply to Northern Virgina, Virtually the only part of the state to have suffered from lines.

Emerging from a closed-door sessions with 10 state legislative leaders Dalton predicted August will be a better month for Northern Virginia drivers. The area was plagued by gasoline lines that gegan in late May and eased after the first week of July.

"I don't believe we'll have the lines situation in Orthern Virginia like we saw in June and the first half of July," Dalton said. He promised to monitor gasoline supplies "on a day-to-day basis to see to it that lines will not appear anywhere in the state.

State Sen. Adelard L. Brault of Fairfax, Democratic majority leader, and Del. Vicent F. Callahan Jr. of Fairfax, Republican Caucus leader, both of whom attended the meeting, pronounced themselves satisfied.

"I'm hopeful we won't get any less total gallons then last month," said Brault, one of many area politicians who accused Dalton of aggravating the gasoline crisis in June by reacting too slowly to worsening lines. "My feeling is he (Dalton) did today what he should have done."

Callahan, who also criticized the speed of Dalton's response last month, said, "Our ultinate objective was to remove the lines, and as long as the lines are not thee, we won't complain."

Distribution of setaside gasoline has been a constant political headache for Dalton since preliminary figures for May and June indicated a disproportionate share was going somewhere besides Northern Virginia.

The figures caused a howl of protest from Northern Virginia politicians of both parties. Coupled with lengthening lines at area stations, that protest led Dalton's energy director, George L. Jones, to pledge that Northern Virginia would get 40 percent of the state's July seaside supply.

Figures released yesterday by the energy office show Northern Virginia got 3.8 million gallons of setaside gasoline in the first three weeks of July, nearly double the 2 million gallsons the area received in June.

But pledges to Northern Virginia have led Virginia politicians elsewhere to protest. At yesterday's meeting, according to participants, both Speaker of the House John Warren Cooke (D-Mathews) and House Majority leader A. L. Philpott (D-Bassett) complained their rural areas were suffering gasoline shortages and needed more state relief.

"There's no question the governor's been under a lot of pressure from all sides," said Brault.

Dalton's press secetary, Paul Edwards, said the governor's officer had received numerous complaints from residents and officials outside Northern Virginia who feel the area has received too much of the state's supply. But Edwards said politics was not behind Dalton's refusal to commit 40 percent to the area again in August.

"When the long lines hit Northern Virginia, the setaside was the only tool we had, so we made that commitment," said Edwards. "How that the lines are gone, the rational thing to do Is to allocate the gas to those who need it and not make an advance commitment to a particular region or locality."

Although Dalton credited the setaside allocations with easing the lines, Edwards and Callahan said other factors, such as the odd-even system, staggered service station hours and the improved ovrall supply picture were much more responsible.

Callahan said he Didn't think the Republican governor's handling of the gasoline crisis ultimatrly would prove to be a political liability.

"It's a two-edged sword," Callahan said. "If the Democrats start pointing the finger at him (Dalton), the Republicans can point their finger right back at Washington and the Carter administration, where the real energy problem is."